Voice of the Earth and Space Science Community

As Northern Californians picked up the pieces and cooled their nerves on the afternoon of August 24th, just hours after being jostled or lurched from bed by the 3:20am magnitude 6.0 South Napa quake, a satellitean aircraft whizzing by overhead snapped a shot of the scene. Check out some of these remarkable scenes within it that show damage, response, and recovery.

The image is now visible in Google Earth, and in Google Maps on mobile devices–surely it’s coming to the browser version soon. Peruse it yourself, but have a look at the highlights below:

Caltrans worked fast that day to get the region up and running. Even for such a modest quake they had a lot of bridges to inspect and a lot of road offsets to patch. Farther south we see two big asphalt-filled dump trucks patching up another site on their days-long tour of broken roads, the beginning of months and $5.3 million of work:

Other rapid responders included the scientists that mobilized from nearby institutions and agencies to go find answers to everyone’s questions. Extent of damaged region, causative fault, risk of afterslip, risk of aftershocks, risk of more and bigger earthquakes… these are all pressing questions that of course in hindsight we have answers to. On the day of the earthquake, the extent of the rupture was just being discovered, and field scientists were beginning to spot the dramatic effects of ongoing “afterslip.” In this early afternoon aerial pass, we can spot my own officemates out with the research group field vehicle, measuring offsets visible of the road, fence line, driveway pavers, and vine rows.

But utility crews and scientists weren’t the only ones dealing all day with the effects of the quake. Violent shaking unsettled the citizens of Napa, and the image captures a more poignant scene of a neighborhood grappling with the quake’s effects. This portion of the scene is striking to me; there’s a lot going on. The fault rupture runs through the center, delineated by arrows at the top and bottom of the screenshot. Its effects on infrastructure are clear, where roads and sidewalks have been buckled and subterranean pipes ruptured, spewing wet sand across the road. Utility trucks abound, addressing these issues and surveying the homes that straddle the fault line (PG&E trucks are light blue). Meanwhile the residents of one torqued house unload all their belongings into a trailer, filling the front yard with furniture with the help of their neighbors in order to vacate the structure before it’s deemed uninhabitable.

From this vantage a couple things stand out: the streets have already been cordoned off–that happened early on upon discovery of this damage–and a press and emergency crew camp set up across from the damaged structure. In addition, you can see just how much traffic is moving around the city, crossing a bridge no less! This is the reality of an earthquake in which there’s a great deal of damage but very little loss of life: people will be moving around, whether it’s to get supplies for themselves (for clean-up OR survival), to check on family and friends, or just to lookie-loo. This is a big management challenge for emergency response operations that requires truly rapid assessment of damaged and undamaged structures. It also makes clear how important it is to check on lifelines to a city and have alternatives if, for example, that bridge had suffered more damage than it did. (Check out the CA Earthquake Clearinghouse’sonline map interface to see photos from structural surveys and inspections following the quake.)

Satellite Aerial imaging provides a spectacular resource to earthquake responders of all stripes. It is fortunate to have such a timely acquisition, which is often difficult with existing satellite platforms. Napa’s climate also avoided one of the other major limitations of airborne imaging data: cloud cover.

*Update 10-24-14 16:02 UTC: I’ve learned from Tim Dawson at the CGS that this Google orthoimagery was actually captured from an airplane after discussions between the Google crisis response team and the USGS & CGS. Testament to the power Google has for rapid mobilization, and commendable cooperation among relevant agencies. No wonder they got around the obstacles of satellite data.

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About Me

Austin Elliott is a Postdoctoral Researcher at the University of Oxford. He researches the history of earthquakes in the landscape and what we can learn about them from satellites. In this blog he highlights developments in earthquake science, notable mitigation efforts around the world, and media that unveil and illuminate the phenomenon of earthquakes.

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